This anatomical investigation employs Golgi and electronmicro-scopic techniques in an attempt to understand postnatal growth and differentiation of the neurons in the spinal trigeminal nucleus. The objectives of this study are to analyze the histological features of developing neurons in newborn kittens and establish how neuronal cell bodies, their axons and dendrites and neuroglial cells interact with each other. Each disclosure is contrasted with its counterpart in the adult nucleus. These findings will help in understanding how axons and dendrites become accurately oriented with respect to each other and the trigeminal nerve endings so that appropriate synaptic connections in the trigeminal pain-temperature pathways can be established. These studies also seek to establish how spinal trigeminal neurons can grow and differentiate postnatally in the absence of large intercellular spaces.